wrote:

Greetings from the Great snowed in North....

I called Titebond and asked about mech properties
of TB3 glue and heard something I didn't like. I ewas told it
wsnt approved for
structural applications because it creeped over time.. Now
exactly what that relationship is
is is not too clearly defined. It seems that the glue will
exhibit creep under constant loads
over time. This means you dont want to do glue lams for house
parts, but it is unclear
if this applies to airplanes. They dont see stress except when
carrying flight loads, and
the question of duration meeting the meaning of the term "over
time" isnt defined.
I'd build ribs right now with it, but I might use epoxy on the
spars......
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With that message from the Great Snowed-in North, you should be aware
that Leonard Mulholland has used Titebond-III on his Legal Eagle and
Double Eagle wings, which are the only wooden parts. (The other parts
are steel tubing and were assembled using smoke & flames!)

To creep or not to creep, that is the question. But knowing how much
weight was involved in the creep test would be a good place to start.
As I recall, the FPL used something like 200 psi and 80F degrees for
their standard creep test. Leonard's wing has surely seen the 80F
factor a time or two but even the springiest leading edge ply is only
a few pounds, far, FAR away from the factor used by the FPL.

So I THINK Titebond-III is okay... that their definition of 'creep'
will not be a factor in my usage of the adhesive. The tests I have
run -- an some continuing even now -- were started in March of 2007.
(It is now Dec of 2008) Of those completed (ie, tested to
destruction) there was no evidence of creep at the time the ribs were
destroyed. Of those left hanging... I'll have to take them down in
order to use the space... one is supporting a weight of about 200
pounds, the other has the same weight but the rib is oriented
differently. Neither shows any evidence of creep but then, neither
has been subjected to CONSTANTLY high temperatures; only the ambient
temps here at the shop, which have ranged from the 50's to the 80's
with an occasional excursion higher or lower. No creep there, either.

-Bob Hoover